The present invention relates generally to spring-loaded check valves, and more particularly to a check valve loaded by a spring having a substantially constant spring force over a considerable range of its deformation.
There are already known various constructions of check valves which are constructed to permit flow of a fluid therethrough in one direction but to prevent such flow in the opposite direction. To keep the valve member in its closing position until and unless the pressure exceeds the outlet pressure by a predetermined margin, it is already known to use springs or weights which act on the valve member and urge the same toward sealing contact with a valve seat provided in the interior of the valve housing. So, for instance, it was already proposed to use a buckling-type helical spring for this purpose, one end of such a spring being connected to the valve member which is pivotaly mounted in the outlet compartment of the valve housing, while the other end of the spring is secured to a region of the valve housing which is spaced at predetermined distance from the valve member. However, experience with this kind of an arrangement has shown that it is quite difficult to assemble the valve of this construction, inasmuch as the spring has to be pretensioned as it is being mounted in the outlet compartment of the valve housing to assure that the valve member will engage the valve seat with a sufficient amount of force to avoid leakage of fluid past the valve member. It is also already known to use spring-loaded 4-bar linkages for urging the valve member against the valve seat; yet, even such constructions have been proven to be less than satisfactory in terms of operation and particularly ease of assembly.